Process for preparing a viscose spinning solution, fibers formed therefrom and paper containing said fibers



,1967 YOICHI KAJITANI PROCESS FOR PREPARING A VISCOSE SPINNING SOLUTION, FIBERS FORMED THEREFROM I AND PAPER CONTAINING SAID FIBERS Filed OOc. 16, 1964 2 Sheets-Sheet 1 S \M S .30 20 I0 0 Carbon DISH/{Ma INVENTOR ya/O/z) Ma a??? Bymfiwnww ATTORNEYS Dec. 19, 1967 YOICHI KAJITANI 3,359,155

PROCESS FOR PREPARING A VISCOSE SPINNING SOLUTION, FIBERS FORMED THEREFROM AND PAPER CONTAINING SAID FIBERS Filed Oct. 16,1964 '2 Sheets-Sheet 2 mmljq -Z00 Pr: 3s a re 0 20 4b 6b 250 160 /0 A10 160 lomm;

React/'07: 7/7118 INVENTOR ATTORNEYS United States Patent 3,359,155 PROCESS FGR PREPARING A VISCOSE SPINNING SOLUTION, FIBERS FORMED THEREFROM AND PAPER CONTAINING SAID FIBERS Yoichi Kajitani, Saijo, Japan, assignor to Kurashiki Rayon Company Limited, Kurashiki, Japan, a corporation of Japan Filed Oct. 16, 1964, Ser. No. 404,271 Claims priority, application Japan, Oct. 28, 1963, 38/57,821; Dec. 16, 1963, 38/67,:573 12 Claims. (Cl. 162146) The present invention relates to improved cellulose products and a method of producing the same and more particularly to papers having excellent lustre and excellent superficial anti-abrasive strength and a method of manufacturing the same. The invention also relates to improved viscose rayon fibers and the method of manufacturing the same, more particularly to fiat and hollow viscose rayon fibers having self-bonding property and a method of manufacturing the same, and in addition the invention relates to viscose suitable for manufacturing said improved rayon yarns and a method of manufacturing the same.

The method of manufacturing viscose rayon has been known since long years, however, it had been difficult to produce papers by using raw materials consisting of viscose rayon fibers manufactured by a conventional method. The difiiculty was due to the fact that hitherto known viscose rayon can not be fibrillated by beating, like pulps, hence conventional viscose rayon fibers lacks in selfbonding property. Accordingly, in order to manufacture papers from the hitherto known viscose rayon fibers, it was necessary to add a binding agent such as polyvinyl alcohol or self-bonding fibers such as polyvinyl alcohol fibers.

A method of manufacturing hollow rayon yarns for clothes by spinning viscose mixed with foaming agents like sodium carbonate is known. But as fibers produced by such a method are not flat fibers, such fibers have no self-bonding property, accordingly without adding a binding agent, it is impossible to manufacture papers by using such fibers.

On the other hand, a method of manufacturing fiat and self-bonding viscose fibers has been developed recently, which comprises spinning viscose in admixture with surface active agent, modifier and gases welldispersed in the mixture by stirring, or by spinning viscose containing derivatives of cellulose ethers in admixture with surfactant, modifier and also gases well-dispersed by agitating. It is possible to manufacture papers by using said flat and self-bonding fibers obtained by the above methods. The above method of manufacturing the fiber, however, requires to spin viscose having a relatively low cellulose content, a high alkali content, and an expensive modifier into a spinning bath having a low concentration of sulfuric acid and a high concentration of zinc sulfate, hence the method has disadvantage of high manufacturing cost. Further, a considerably large amount of gas should be mixed and dispersed in the viscose and it required special equipments and techniques to disperse a large quantity of gas uniformly throughout the viscose, and papers manufactured by using such fibers have weak superficial anti-abrasive strength.

Therefore, the principal object of the invention is to provide papers having excellent luster and high strength, especially high superficial anti-abrasive strength, and also a method for manufacturing the same.

Another object of the invention is to provide flat and hollow viscose rayon fibers and a method to manufacture the same.

Still another object of the invention is to provide fibers "ice having excellent web-forming afiinity and self-bonding property and a method of its manufacture.

Still further object of the invention is to provide fibers suitable to manufacture papers, which can be readily dispersed in water and have good water retention without necessitating beating, and a method of manufacturing the same.

Still more object of the invention is to provide fibers suitable to manufacture papers having excellent properties, especially extraordinary good luster, from said fibers alone or from a mixture of said fibers with other papermaking materials, and to provide a method of manufacturing the same.

For a better understanding of the invention reference is made to the accompanying drawings, in which,

FIG. 1 is a graph illustrating the variation of the boiling point of a mixture of carbon disulfide and acrylonitrile against the mixture ratio of the two, and

FIG. 2 is a graph illustrating the relation between the pressure in the reaction vessel and the reaction time when alkali cellulose is reacted by CS and C I-I CN simultaneously in vacuo within said vessel.

According to the invention, the improved viscose rayon fibers are manufactured by obtaining a viscose by dissolving the product of a simultaneous reaction of carbon disulfide and acrylonitrile with alkali cellulose in a dilute alkali solution under at least atmospheric pressure, subjecting deaeration and ripening to the resulting solution under at least atmospheric pressure, then giving shocks to said solution after reducing the pressure to atmospheric pressure to foam the air dissolved in the solution and to disperse said foamed air in the solution, and thereafter spinning said viscose solution into a spinning bath.

Papers having excellent luster and high strength, specially extraordinary high anti-abrasive superficial strength can be manufactured from the improved viscose rayon fibers alone or in admixture of other paper-making fibers.

Alkali cellulose can be obtained by steeping pulps in an alkali solution and then pressing and shredding the steeped pulps. According to the invention, the alkali cellulose thus obtained is reacted with carbon disulfide and acrylonitrile simultaneously after aging or without aging. Viscose containing 4-10% of cellulose and 38% of total alkali is obtained by dissolving the product of the above reaction in a dilute alkali solution under atmospheric pressure or higher pressure. The composition of the viscose to be used in the invention can be either that of a viscose used in the production of ordinary viscose fibers or that of a viscose having a low ratio of alkali to cellulose in the order of 0.5-0.75.

The aging period of viscose is preferred to be as short as possible. It is necessary to perform deaeration and ripening under atmospheric or elevated pressure. When viscose is manufactured by dissolving cellulose xanthate, a large amount of air is inevitably mixed in the viscose during stirring and a great number of air bubbles of various sizes are contained in the viscose directly after the dissolution and stirring, hence deaeration and aging are carried out under reduced pressure to eliminate said air bubbles mixed in the viscose in conventional method of manufacturing rayon fibers. The inventor, however, has found that the viscose directly after the dissolution containing not only numerous air bubbles of various sizes but also a substantial amount of air dissolved in viscose itself. Accordingly, the conventional deaeration and aging under reduced pressure apparently enables elimination of not only the large number of air bubbles contained in viscose, but also the air dissolved in viscose can be removed after once foamed out of the viscose. On the other hand, if the deaeration and aging are carried out under atmosperic pressure instead of a reduced pressure, the air bubbles contained in the viscose will defoam from the surface of the viscose as time elapses but the air dissolved in the viscose will not be eliminated. If said deaeration and aging are carried out under elevated pressure, all or a part of a great number of air bubbles, which are mixed in the viscose when partially cyanoethylated cellulose xanthate is dissolved, can be dissolved in the viscose and the remaining air bubbles can be defoamed from the surface of the viscose in the same manner as in the case of deaeration and aging under atmospheric pressure. Accordingly, the viscose deaerated and aged under atmospheric, preferably elevated pressure, does not contain air bubbles as viscose deaerated and aged under reduced pressure, however, the former contains a great amount of dissolved air whilst the viscose deaerated and aged under reduced pressure contains no dissolved air.

While the higher the pressure at deaerating and aging is the larger is the amount of air dissolved, a hollow fiber of great flatness may be obtained by the invention even when aging is performed under atmospheric pressure. Either atmospheric 01- elevated pressure may be employed depending upon the denier of fiber, the amount of acrylonitrile and CS added, the desired properties of produced paper and other requirements. A pressure exceeding 5 kg./cm. in gauge pressure is not necessary for aging under pressure.

To dissolve air into previously prepared viscose by providing air from outside, there is an inherent difficulty in obtaining uniform air distributions throughout the viscose.

If the partially cyanoethylated cellulose xanthate is dissolved under elevated pressure instead of atmospheric pressure, the amount of air dissolved in the viscose will be increased further. The viscose containing dissolved air is given shocks, for example, by either stirring or vibrating, to foam the dissolved air as bubbles. To foam the dissolved air in viscose, it is necessary to give suitable shocks to the viscose either after the pressure is reduced to atmospheric pressure in the case of the pressured viscose or without changing pressure in the case of the viscose defoamed and aged under atmospheric pressure. For example, while bubbles may be formed easily by trans ferring viscose from one vessel to the other or dropping viscose from a suitable height, it is preferable for foaming to agitate viscose by means of a suitable stirring apparatus or to vibrate viscose continuously by means of a suitable vibrator.

The bubbles thus formed have properties different from the bubbles obtained by intentionally blowing in air from outside, because the former are produced from the latent air dissolved in the viscose by shocks. The bubble-dispersed viscose thus obtained comprises only uniform sized fine bubbles most suitable for spinning and it has an eX- cellent spinability.

The latent air will evolve as very fine bubbles at first, which are not visible by naked eyes, then the bubbles will shortly grow to the size suitable for the production of hollow fibers and such grown bubbles will be dispersed throughout the viscose. Since the viscose is a liquid having a very high viscosity compared with water, the fine bubbles thus evolved will be dispersed in the viscose and retained there for a long period without joining with each other. In generating bubbles from the dissolved air by shocks, it is necessary to avoid the entrance of external air and the air bubbles previously existing in the Viscose should have been removed almost throughly prior to the application of shocks. Such bubbles are not necessary to obtain a hollow rayon of great flatness, since they only result in the break of single filament and the clogging of nozzle at spinning. A conventional spinning bath containing 515% of sulfuric acid, -30% of sodium sulfate and 0.5-5 of zinc sulfate may be used while the composition of the spinning bath is not particularly specified. The suitable temperature of the spinning bath in 45-70 C.

The fibers manufactured by means of said method using less than 3% of acrylonitrile based on the weight of cellulose are insufficient in self-bonding property. If more than 40% of acrylonitrile based on the weight of the cellulose are reacted with the alkali cellulose, the fibers obtained will be water-soluble or have an excessive degree of swelling, and they are not suitable for manu facturing papers.

As for the degree of cyanoethylation, suitable content of cyanoethyl radicals is 0.05-0.5 based on the quantity of anhydrous glucose units of cellulose molecule and as explained above, less than 0.05 of cyanoethyl radicals result in an insufiicient adhesiveness as binders whilst more than 0.5 result in water-soluble fibers, which are not suitable. The most suitable range is 0.1-0.4.

The fibers manufactured by means of said method by using less than 20% of acrylonitrile based on the weight of cellulose, said acrylonitrile being to react with said alkali cellulose, are suitable for manufacturing papers with said fibers alone. The fibers manufactured by using more than 20% and less than 40% of acrylonitrile based on the weight of the cellulose, said acrylonitrile reacting with said alkali cellulose, are suitable for manufacturing paper in admixture with other paper-making materials.

The fibers suitable for theproduct of the invention can be manufactured also by reacting the viscose, which is produced by dissolving sodium cellulose xanthogenate obtained by reacting alkali cellulose with carbon disulfide in water or in a dilute alkali solution, with acrylonitrile, defoaming and aging the resulting solution of the above reaction under atmospheric pressure or elevated pressure, giving impacts to said solution under atmospheric pressure to foam the air dissolved in said solution and to disperse said air in said solution, and thereafter spinning said foamed solution into a spinning bath. The reaction of the viscose with acrylonitrile after said viscose once produced, however, results in a loss of 2050% of the acrylonitrile, because Na CS and Na s cause following chemical reactions:

2CH2=CH-CN NazCSs 2Hfl0 CHa CHrCN ZNaOH S OS:

CHz-CHrCN CHa-CHz-CN ZCHFCHCN Nazs 21120 ZNEOH S CHz-CHz-CN CHTCHTCN S ZNaOH ZHzO CH2-CH2-CN CH2-CH2-COONa ZNHs S CHz-CHz-COONB Therefore, the above method including a reaction of the viscose with acrylonitrile has a disadvantage that the quantity of acrylonitrile available for the reaction with the cellulose is reduced to -50% According to the invention, xanthogenation and cyanoethylation of the alkali cellulose are conducted simultaneously by means of CS and C H CN, and since reaction products of CS and NaOH, namely Na CS and Na S, do not exist or may exist only a very little so that substantially no consumption of acrylonitrile, hence the quantity of acrylonitrile available for the reaction with cellulose attains to 98-l00%, which is a very high rate of utilization.

Referring to FIG. 1, when the mixture ratio of acrylonitrile based on the quantity of carbon disulfide is less than 1.5 in the mixture of carbon disulfide and acrylonitrile, the mixture of carbon disulfide and acrylonitrile becomes an azeotropic mixture having a boiling point lower than that of the carbon disulfide alone. Then, if the mixture ratio of acrylonitrile based on the quantity of carbon disulfide is selected to be less than 1.5 in the simultaneous reaction of acrylonitrile and carbon disulfide with alkali cellulose, the vapor pressure is raised and the reaction velocity becomes much quicker as can be easily seen from FIG. 2. The manner in which the reaction velocity varies is shown in FIG. 2, in which the curve 1 illustrates the variation of pressure within a vessel when alkali cellulose is reacted with a mixture of 45% of carbon disulfide and 30% of acrylonitrile, both based on the quantity of the cellulose, and the curve 2 illustrates the pressure variation when only 45% of carbon disulfide is reacted with the alkali cellulose. Judging from FIG. 2, the reaction with the mixture of carbon disulfide and acrylonitrile reaches an equilibrium of pressure in 70-80 minutes for the termination of the reaction, whilst the reaction with carbon disulfide alone takes 150-160 minutes to finish the reaction. The negative values in the pressure indication in FIG. 2 show that the reaction is carried out in vacuo.

In the case of simultaneous reaction of CS and C H CN with alkali cellulose, the amount of CS may be at least based on the weight of the cellulose. The reason for that such a small quantity of CS is sufficient is due to the fact that the simultaneous reactions of carbon disulfide and acrylonitrile causes the xanthogenation and cyanoethylation of the alkali cellulose at the same time and both of the latter two make alkali cellulose soluble. Accordingly, when there is a relatively large amount of acrylonitrile necessary amount of carbon disulfide is small, and for relatively small amount of acrylonitrile much carbon diuslfide is required. In any case, however, it is not necessary to increase the quantity of carbon disulfide above 80% based on the weight of cellulose, and the amount exceeding 80% is a complete waste. The reaction of alkali cellulose with a mixture of 10-80% of carbon disulfide and 3-40% of acrylonitrile, both based on the weight of the cellulose, will be completed in 60 to 120 minutes at 25 C.

Since the tenacity of the fibers spun in the manner as described above is increased by giving a high stretch on the spinning process but the flatness of fibers is lowered, 10-l00% stretch preferably 30-60% stretch may be taken. The second bath may or may not be used in the spinning process.

According to the invention, to give sufiicient waterretaining and self-bonding properties to the fibers and to make said fibers suitable for the manufacture of papers, it is necessary that the major axis is more than 7 times as long as the minor axis in the cross section of the fiber and the hollow factor of the fiber must be more than 50%. If the degree of the flatness, as defined above, is less than 7 times, various properties described hereinbefore are not attained, hence the desired papers can not be obtained. Here, the hollow factor is meant by the ratio of the hollow filament number to the total filament number, and if the hollow factor is less than 50% the self-bonding property will be reduced. The preferable degree of flatness and hollow factor are more than 8 times and more than 80% respectively.

According to the invention, the available size of the fiat and hollow fibers is 0.5-20 denier, and in particular 1.2-12

denier is preferable. Fibers of less than 0.5 denier are I difiicult to spin and they do not produce strong papers, and at above 20 denier, the self-bonding property is reduced. According to the invention, the fiber length of the flat and hollow fibers and other fibers to be mixed thereto may be 2-40 mm., and a suitable fiber length for paper making machine is 2-25 mm. For manual operation, those of 25-40 mm. may be used and with such fibers paper sheets having a peculiar texture are obtained by using long fibers. With less than 2 mm. of the fiber length, the

strength of the produced paper is not sufiicient, and with more than 40 mm. of the fiber length, the dispersion is inferior to cause difliculty in paper making and uniform paper sheets can not be obtained.

In refining process, the desulfurization process should 6 be omitted, because it is impossible owing to a large swelling. A short cut fiber decreases the strength of paper and a long cut fiber can not be well dispersed to yield a uniform paper, so that the cut length of 1-20 mm., preferably 3-7 mm. should be adopted. I

While a sufiiciently strong paper may be obtained by using the fiber prepared by the process according to the invention alone for making paper, if desired, adhesive such as polyvinyl alcohol fiber or powder may be added or natural fiber such as pulp, mitsumata, kozo, ganpi, manila hemp etc. or synthetic fiber such as nylon, vinylon etc. may be used in admixture with said fiber.

Since the natural fibers have self-bonding and paper making ability, 0 to 97% of natural fibers can be mixed to the fibers which are manufactured by the method of the invention. Synthetic fibers have no self-bonding property, hence it is proper to mix 0-30% of synthetic fibers to the fibers according to the invention when paper is made without adding any adhesive. If the mixture ratio of the fibers of the invention is 100-60% of the total fibers, the produced paper will shine from its entire surfaces, and at 60-30% the produced papers will have lusters and textures as if the same amount of glass fibers were scattered. At less than 3%, said luster effects are greatly reduced.

The advantages brought about by the invention have been described hereinbefore, but the following features can be attributed to the invention:

(1) The cost of manufacturing is very small and the fibers of the invention are more economical compared with the self-bonding rayon for papers obtained by a known viscose method. Further, there are less troubles in manufacturing such fibers.

(2) The flatness and contact area between fibers are large and the Web-forming property is excellent so that a strong paper may be obtained from the fibers of the invention alone.

(3) The water-dispersibility and water-retention are good, hence a heating process can be dispensed with and the paper-making may be simplified.

(4) The paper according to the invention has excellent luster so that various high class papers, art papers and decorative papers which have a high surface strength (superficial anti-abrasive strength of the paper) and there is very little fluff.

The invention will be further described in detail by the following examples, which are not limitative of the invention.

Example 1 An alkali cellulose obtained in a conventional method was aged, a mixture of 35% by weight of CS and 30% by Welght of acrylonitrile based on the weight of cellulose were added to the alkali cellulose and reacted at 25 C. for 2 hours. After the reaction, the resulting product was dissolved in a dilute alkali solution under atmospheric pressure to form a viscose containing 8.5% of cellulose and 5.0% of total alkali.

The viscose was filtered, deaerated and aged under atmospheric pressure, and discharged when the ammonium chloride value became 18 cc., delivered to a tank in which the dissolved air was evolved and dispersed by stirring at a revolving speed of. r.p.m. bymeans of a propeller stirrer for 5 minutes. It was then spun in a coagulating bath containing 9% of sulfuric acid, 1.5% of zinc sulfate and 28% of sodium sulfate at 48 C. to yield a filament of 8 denier. The fibers thus obtained were thoroughly washed with water and cut into 10 mm. Then 30% of said product and 70% of pulp beaten are mixed and made into paper according to a conventional process.

The paper thus obtained comprised of fibers having a degree of cyanoethylation of 0.21, a mean degree of flatness of 9.2 times, and a hollow factor of 89%, and the paper had a beautiful luster, a breaking length of 4.8 km. and a tear factor of 142. The paper made from 100% 7 pulp by the same process had no brightness and breaking length of 2.9 km. and tear factor of 114.

Example 2 A mixture of 38% of CS of acrylonitrile was reacted with alkali cellulose to form a viscose containing 8% of cellulose and 5.5% of alkali in the same manner as in Example 1. The viscose was retained under a pressure of 4 kg./cm. for 10 hours to defoam, then the pressure was reduced again to atmospheric pressure and stirred for 3 minutes at 140 rpm. of a propeller stirrer to evolve and disperse the dissolved air and a filament of 5 denier was spun in a spinning bath of the same composition as in Example 1. The fibers was cut into 5 mm. and a paper containing said yarn alone was made.

The paper thus obtained comprised fibers having a degree of cyanoethylation of 0.18, an average flatness of 8.6 times, and a hollow factor of 91%. A reference paper was made from fibers prepared by the same procedure as mentioned above without addition of acrylonitrile. The properties of both papers are shown in Table l.

To alkali cellulose were added 42% of CS and of acrylonitrile, both based on the weight of cellulose, simultaneously. The reaction product obtained by reacting said mixture at 25 C. for 2 hours was dissolved to yield a viscose containing 7% of cellulose and 6% of alkali. The viscose was defoamed and aged under a pressure of 3 kg./cm. then the pressure was reduced again to atmospheric pressure when the Hottenroth value was 12, and a slight vibration in the order of 1,000 cycles/ min. was applied for 60 minutes to the viscose through the vessel by means of a vibrator to evolve bubbles.

The viscose thus obtained was stirred to disperse bubbles uniformly, then spun in a spinning bath containing 8% of sulfuric acid, 3% of zinc sulfate and 25% of sodium sulfate at 55 C., the fiber thus obtained was stretched up to 40% in the second bath and was taken up at a speed of 45 m./min. to yield flat and hollow filament of 1.5 denier. The fibers thus obtained had a degree of cyanoethylation of 0.17, an average flatness of 8.4 times, and a hollow factor of 74%.

The fiber was cut to 4 mm. and made into a paper by a conventional process. A strong paper of high brightness having a breaking length of 4.3 km., a tear factor of 412 and an excellent anti-abrasive strength was obtained. For comparison, fibers were made according to the same process without adding acrylonitrile and a paper was prepared from said fibers which showed a breaking length of 1.8 km. and a tear factor of 153.

Example 4 A mixture consisting of 30% of carbon disulfide and 36% of acrylonitrile, both based on the weight of cellulose, was added to alkali cellulose produced by a conventional process, and the mixed product was reacted at 25 C. for 2.5 hours. The reaction product thus obtained was treated in the same manner as in Example 1, then spun at 57 C. in a spinning bath containing 10.3% of sulfuric acid, 2.1% of zinc sulfate, and 27% of sodium sulfate to obtain fibers having a single filaments of 16 denier, the degree of cyanoethylation of 0.21, flatness of 8.3 times, and hollow factor of 90%. The fibers thus obtained were washed thoroughly with water and then cut to 20 mm. lengths. A mixture "consisting of 10% 'of' said 'fibers and 90% of beaten pulp was made into a paper by a conventional process.

In the paper thus obtained, the flat and hollow fibers of 16 denier were firmly bonded with the pulp. For the sake of comparison, another paper wa manufactured by mixing flat and hollow fibers produced in the same manner as the above without adding acrylonitrile with pulp. In the latter paper, said flat and hollow fibers dropped off easily from said paper by friction.

Example 5 A mixture consisting of 15% of carbon disulfide and 40% of acrylonitrile, both based on the weight of cellulose, Was added to the alkali-cellulose produced by a conventional process, and the mixed product was reacted at 25 C. for 2 hours. The reaction product thus obtained was treated in the same manner as in Example 1, and fibers having a single filaments of 4 denier and length of 4 mm. were obtained.

Table 2-A shows the properties of said fibers and the properties of the paper manufactured by using said fibers.-

Example 6 In Example 5, the quantities of carbon disulfide and acrylonitrile were changed to 23% and 34% respectively. The properties of the resulting products are shown in Table 2-B.

Example 7 In Example 5, the quantities of carbon disulfide and acrylonitrile were changed to 30% and 25% respectively. The properties of the resulting products are shown in Table 2-C.

A mixture consisting of 40% of the flat and hollow fibers having a fineness of 1.5 denier, which were manufactured by the method of Example 3, and 60% of mitsumata fibers were made into a paper by a conventional process. Properties of the papers thu obtained are shown in Table 3-A.

Example 9 A mixture consisting of 20% of the flat and hollow fibers having a fineness of 1.5 denier, which were prepared by the method of Example 3, 20% of conventional viscose rayon fibers (1.5 denier, 4 mm. length), and 60% of beaten pulp was made into a paper. Properties of the papers thus obtained are shown in Table 3-B.

Example 10 A mixture consisting of 7% of flat and hollow fibers having a fineness of 5 deniers, which were prepared by the method of Example 5, of mitsumata, and 13% of manila hemp was made into a paper. Properties of the papers thus obtained are shown in Table 3-C.

TABLE 3 Sample Breaking Tear Factor Luster length (k'm.)

7. 9 380 Very good. 5. 4 242 Good. 8.2 420 Do.

What I claim is: 1. A process for the preparation of a viscose spinning solution, comprising dissolving in a dilute alkali solution under at least atmospheric pressure the products of a simultaneous reaction among carbon disulfide, acrylonitrile and alkali cellulose, the amount of acrylonitrile ranging from between about 3 percent and 40 percent by weight of cellulose and the amount of carbon disulfide being at least about 10 percent by weight of cellulose, deaerating and ripening the resultant solution which contains both dispersed and dissolved air therein such that said dispersed air is at least partially selectively evolved and the said dissolved air is retained, the portion of the said dispersed air not evolved itself being dissolved and also being retained, and thence foaming the said dissolved air and uniformly dispersing the said air thus foamed in the solution.

2. The process as defined by claim 1, wherein the dispersed air is selectively evolved and the dissolved air is retained by deaerating and ripening at a pressure Which ranges from between atmospheric pressure and 5 kg./cm.

3. The process as defined by claim 2, wherein the dissolved air is foamed and the air thus foamed is uniformly dispersed in the solution by shocking the said solution under atmospheric pressure.

4. The process as defined by claim 3, wherein the viscose solution obtained contains from about 4 percent to about percent cellulose and from about 3 percent to about 8 percent total alkali, wherein the degree of cyanoethylation ranges from between about 0.05 to about 0.5, based on the quantity of anhydrous glucose units in the cellulose molecules, and further wherein the amount of carbon disulfide ranges from between about 10 percent to about 80 percent by weight of the cellulose.

5. The process as defined by claim 3, wherein the said shocking is effected by stirring.

6. A process for the preparation of viscose rayon fibers, comprising spinning the viscose solution prepared by the process of claim 1 into fibers.

7. The process as defined by claim 6, further comprising stretching the resultant fibers from about 10 percent to about 100 percent.

8. Flat, hollow, self-bonding, partially cyanoethylated uniform viscose rayon fibers readily dispersed in water, said fibers exhibiting a degree of cyanoethylation ranging from between about 0.05 to about 0.5 based on the quantity of anhydrous glucose units in the cellulose molecule, major axes more than 7 times as long as minor axes in fiber cross-section, a size ranging from between about 0.5 to about 20 denier and being at least 50 percent hollow in cross-section, and said fibers having been manufactured via the spinning of a viscose solution prepared by dissolving in a dilute alkali solution under at least atmospheric pressure the products of a simultaneous reaction among carbon disulfide, acrylonitrile and alkali cellulose, the amount of acrylonitrile ranging from between about 3 percent and 40 percent by weight of cellulose and the amount of carbon disulfide being at least about 10 percent by weight of cellulose, deaerating and ripening the resultant solution which contains both dispersed and dissolved air therein such that said dispersed air is at least partially selectively evolved and the said dissolved air is retained, the portion of the said dispersed air not evolved itself being dissolved and also being retained, and thence foaming the said dissolved air and uniformly dispersing the said air thus formed in the solution.

9. High strength, high luster, high superficial abrasion resistant paper comprised of the viscose rayon fibers as defined by claim 8, each having a length of from between about 2 mm. and 40 mm.

10. Paper comprised of from between about 3 percent to about 100 percent of the viscose rayon fibers as defined by claim 8, each having a length of from between about 2 mm. and 40 mm., and from between about 0 percent to about 97 percent natural fibers.

11. Paper comprised of from between about percent to about 100 percent of the viscose rayon fibers as defined by claim 8, each having a length of from between about 2 mm. and 40 mm., and from between about 0 percent to about 30 percent synthetic fibers.

12. The product of the process as defined by claim 1.

References Cited UNITED STATES PATENTS 2,484,012 10/1949 Calhoun 260-218 3,116,199 12/1963 Cruz et al 162-157 3,173,830 3/1965 Wise et a1 162-157 3,223,581 12/1965 Sommer et al. 162-157 3,146,116 8/1964 Bates 264182 X 3,235,642 2/1966 Blomberg 264-182 FOREIGN PATENTS 1,368,694 6/1964 France.

865,339 4/1961 Great Britain.

945,306 12/1963 Great Britain.

S. LEON BASHORE, Primary Examiner. 

1. A PROCESS FOR THE PREPARATION OF A VISCOSE SPINNING SOLUTION, COMPRISING DISSOLVING IN A DILUTE ALKALI SOLUTION UNDER AT LEAST ATMOSPHERIC PRESSURE THE PRODUCTS OF A SIMULTANEOUS REACTION AMONG CARBON DISULFIDE ACRYLONITRILE AND ALKALI CELLULOSE, THE AMOUNT OF ACRYLONITRILE RANGING FROM BETWEEN ABOUT 3 PERCENT AND 40 PERCENT BY WEIGHT OF CELLULOSE AND THE AMOUNT OF CARBON DISULFIDE BEING AT LEAST ABOUT 10 PERCENT BY WEIGHT OF CELLULOSE, DEAERATING AND RIPENING THE RESULTANT SOLUTION WHICH CONTAINS BOTH DISPERSED AND DISSOLVED AIR THEREIN SUCH THAT SAID DISPERSED AIR IS AT LEAST PARTIALLY SELECTIVELY EVOLVED AND THE SAID DISSOLVED AIR IS RETAINED, THE PORTION OF THE SAID DISPERSED AIR NOT EVOLVED ITSELF BEING DISSOLVED AND ALSO BEING RETAINED, AND THENCE FOAMING THE SAID DISSOLVED AIR AND UNIFORMLY DISPERSING THE SAID AIR THUS FOAMED IN THE SOLUTION. 